Figure 1.

Postnatal development of projections from PaS to MEC. The presynaptic side. A–C, Representative grayscale inverted images of an area in MEC showing labeling of parasubicular axons in layers I-III in MEC at (A) P5, (B) P12, and (C) P20. A′, B′, C′, Higher-magnification images of areas indicated with white boxes in A–C. Indicated are examples of varicosities, likely reflecting presynaptic elements (white arrowheads) and axonal branching points (blue arrowheads). Insets, The anterograde tracer injection sites in PaS. Dashed lines indicate brain areas and layers. Scale bars: A–C, 500 μm; A′–C′, 100 μm. Sub, subiculum.